Mitochondria are the organelles of cellular respiration. Carnitine transports fatty acids into mitochondria as fuel and is involved in energy production. Once in the mitochondria fatty acid chains are broken into two-carbon acetyl-CoA units (a process known as β-oxidation), acetyl-CoA can be converted to ATP via the citric acid cycle and oxidative phosphorylation.
Cardiolipin is a component of the mitochondrial membrane and is involved in maintaining mitochondria membrane potential and mitochondrial activity, particularly at the level of fatty acid, β-oxidation processes.
Free radicals are molecules containing unpaired electrons. These unpaired electrons cause oxidative damage in cells and are passed from molecule to molecule turning the recipient into a free radical and neutralizing the donor. In the case of lipid peroxidation, there is a chain reaction which involves both damage and passing of radicals.
Cellular macromolecules are vulnerable to free radical damage: lipids, proteins and nucleic acids can all be damaged. Free radical damage contributes to: cardiovascular disease, cancer, neurodegenerative diseases, inflammatory diseases and other age related degenerative diseases.
Mitochondria are a major source of free radicals and much free radical damage occurs to mitochondrial membranes and mitochondrial DNA due to the mitochondria's own oxidation by products. Mitochondria decay with cellular aging (Shigenaga et. al. 1994, PNAS 91, 10771). Mitochondrial decay is accompanied by a reduction in cardiolipin levels and an increase in free radicals and harms all cellular processes.
Administration of the acetylated version of carnitine, acetyl-L-carnitine, and restores normal cardiolipin concentration in the mitochondria and reactivates mitochondrial activity, including the fatty aid β-oxidation processes. Acetyl L-carnitine also enhances mitochondrial activity by promoting the utilization of the glycolytic pathway for ATP production.
Acetyl L-carnitine can be used to help prevent neuronal lesions or chronic neuronal degeneration; to protect cerebral tissue from damaging peroxidative events; to treat muscular functional deficits and also in the regulation of insulin activity (Patent PCT/IT99/00268 Antioxidant composition comprising acetyl L-carnitine and alpha-lipoic acid).
Carnitine and carnitine derivatives have been used as metabolites for animals and for human diet and therapy: U.S. Pat. No. 4,687,782 (Nutritional composition for enhancing skeletal muscle adaptation to exercise training); U.S. Pat. No. 4,343,816 (Pharmaceutical composition comprising an acyl-carnitine, for treating peripheral vascular diseases); U.S. Pat. No. 5,560,928 (Nutritional and/or dietary composition and method of using the same); U.S. Pat. No. 5,504,072 (Enteral nutritional composition having balanced amino acid profile); U.S. Pat. No. 5,391,550 (Compositions of matter and methods for increasing intracellular ATP levels and physical performance levels and for increasing the rate of wound repair); U.S. Pat. No. 5,240,961 (Method of treating reduced insulin-like growth factor and bone loss associated with aging).
Carnitine is studied extensively in part because of the important role it plays in fatty acid oxidation and energy production, and because it is a well-tolerated and generally safe therapeutic agent. It is proven treatment in children who have recessive defects in the carnitine transporter system and in individuals treated with pivalate containing antibiotics. Other benefits attributed to carnitine result from the management of secondary carnitine deficiencies. These benefits are supported by preliminary findings and need to be confirmed through well-controlled randomized trials. While there is agreement on carnitine's role as a prescription product for the treatment of primary carnitine deficiencies, its benefits as a dietary supplement in individuals who are carnitine sufficient is debated.
Carnitine is termed a conditionally essential nutrient, as under certain conditions its requirements may exceed the individual's capacity to synthesize it. Carnitine mediates the transport of medium/long-chain fatty acids across mitochondrial membranes, facilitating their oxidation with subsequent energy production; in addition, it facilitates the transport of intermediate toxic compounds out of the mitochondria preventing their accumulation. Because of these key functions, carnitine is concentrated in tissues that utilize fatty acids as their primary dietary fuel, such as skeletal and cardiac (heart) muscle. Dietary sources of carnitine include foods of animal origin, such as meat and dairy products. In general, healthy adults do not require dietary carnitine as carnitine stores are replenished through endogenous synthesis from lysine and methionine in the liver and kidneys. Excess carnitine is excreted via the kidneys. In the US, carnitine is an approved prescription drug for the treatment of primary systemic carnitine deficiency and secondary carnitine deficiency syndromes. Carnitine is also available over-the-counter as a dietary supplement, as an aid to weight loss, to improve exercise performance, and to enhance a sense of well-being.
Carnitine is also used for the following treatments and determinations: 1) the treatment of non-alcoholic steatohepatitis (NASH). Steatohepatitis or fat deposits in the liver can result from obesity, diabetes, long-term use of steroids and the antibiotic tetracycline 2) Identifying the specific acylcarnitine that accumulates in peripheral arterial disease in order to determine the specific metabolic disruption. Patients with peripheral arterial disease, who become symptomatic with claudication, have a marked impairment in exercise performance and overall functional capacity. 3) Determining the benefits of carnitine supplementation in the prevention of osteoporosis in post-menopausal women who depend on life-long thyroid stimulating hormone (TSH)-suppressive L-T4 therapy for the management of thyroid cancer. 4) Determining the benefits of carnitine supplementation as prophylaxis or ancillary therapy of serious hyperthyroidism in elderly patients on the anti-arrhythmic drug amiodarone. 5) Determining whether carnitine supplementation can improve symptoms other than fatigue in cancer patients. In addition, test the interaction between carnitine and anti-neoplastics agents used in cancer treatment.
Alpha-lipoic acid: Although Acetyl L-carnitine may improve mitochondrial function, it may also increase free radical damage due to increased energy production through oxidative phosphorylation. So combining Acetyl L-carnitine and a separate antioxidant, such as lipoic acid, can provide both improved metabolic function and reduced oxidative stress (Patent PCT/US98/12545 Dietary Composition for Enhancing Metabolism and Alleviating Oxidative stress.)
Alpha-lipoic acid and some of its metabolites are active antioxidants in the mitochondria. Lipoic acid is an endogenous co-factor for mitochondrial alpha-keto acid dehydrogenase, which may aid in cellular glucose-dependent ATP production. Lipoic acid also increases intracellular ascorbate and glutathione levels. The antioxidant effect of alpha-lipoic acid may be either direct, as an antioxidant itself, or indirect, via restoration of glutathione and ascorbic acid concentrations.
As described in Patent PCT/IT99/00268, alpha-lipoic acid helps in the prevention of diabetic neuropathies and has neuro-protective capability. Those skilled in the art know that administering Alpha-lipoic acid is effective for treating lipid peroxidation (including neural lesions), diabetic neuropathy, glycosylation/glucose oxidation reactions. Alpha lipoic acid may help prevent diabetes related diseases, by inhibiting the activation of the nuclear transcription factor (NF-kB) by reactive oxygen species which in turn, inhibits the associated cascade of neurotoxic and cytotoxic factors. Many of the complications associated with diabetes, such as neuropathies and ocular cataracts are mediated by reactive oxygen species.
Alpha-lipoic acid inhibits the aldose reductase activated by hyperglycemia, enhances insulin-induced muscular utilization of glucose and, in diabetic subjects, and reduces resistance to the effects of insulin on glucose. The action of alpha-lipoic acid on carbohydrate metabolism is due essentially to its ability to act as a coenzyme in the oxidative decarbohydroxylation of pyruvate and other alpha-ketoacids and, through the acetates, in the activation of the tricarboxylic acid cycle leading to the formation of ATP.
A protective effect of alpha-lipoic acid has also been observed in pancreatic cells placed in contact with inflammatory agents.
Lipoic acid has been used as human nutritional supplement and in dietary prophylaxis and therapy. See, for example, U.S. Pat. Nos. 5,607,980 (Topical compositions having improved skin); 5,472,698 (Composition for enhancing lipid production in skin); 5,292,538 (Improved sustained energy and anabolic composition and method of making); 5,536,645 (Nutritive medium for the culture of microorganisms); and 5,326,699 (Serum-free medium for culturing animal cells).
Supplementation with both lipoid acid and acetyl-l-carnitine is an effective way of improving mitochondrial metabolic function without increasing oxidative stress [PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (USA); Hagen, T; 99(4):1870-1875 (2002)]. ALCAR supplementation in combination with lipoic acid substantially restored spatial memory capacity in experimental rats [PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES (USA); Liu, J; 99(4):2356-2361 (2002)].
Lipoic acid can be obtained in the diet from foods containing high metabolic activity. Meat from heart can contain ten times the amount of lipoic acid as meat from muscle. Spinach is also rich in lipoic acid. Lipoic acid is readily digested, absorbed and transported to tissues. Lipoic acid induces cystine/cysteine uptake, thereby increasing synthesis of glutathione.
Patent PCT/IT99/00268 discloses that a composition comprising acetyl L-carnitine and alpha-lipoic acid is effective in the prevention and/or treatment of tissue damage induced by the presence of free radicals due to environmental pollution; of cerebral or myocardial lesions induced by free radicals after cerebral or myocardial ischemia and as a result of reperfusion; of toxic or diabetic neuropathies, and of metabolic disorders in the glucose utilization.
Either acetyl L-carnitine or alpha-lipoic acid can be used on its own in treating neuropathies or in helping to prevent toxic and metabolic damage, as well as in helping to prevent the neuronal lesions arising from such damage. However, Acetyl L-carnitine and alpha-lipoic acid have a more powerful effect when used together in combination. In particular, Patent PCT/IT99/00268 showed that the combination:
(a) had neuroprotective activity in a cerebral ischemia model. Lesions due to cerebral ischemia are related to the production of free radicals and of nitrous oxide. The combination protected against the toxic action of free radicals and reduced the ischemic area. In view of its antioxidant capability, this composition is also indicated in the prevention or treatment of abnormalities of toxic or anoxic origin related to the release of free radicals in other organs and tissues;
(b) helped control serum glucose in hyperglycemia induced rats, hyperglycemia being one cause of diabetic disease at neural, muscular and endothelial level;
(c) reduced the accumulation of intracellular sorbitol, excess sorbitol being associated with lesions induced by diabetic hyperglycemia;
(d) potentiated the neurotrophic effect of Insulin-like growth factor-1 in vitro, suggesting a potential benefit to pathological abnormalities related to ageing, such as neuro-degenerative disorders;
(e) improved neuromuscular conduction velocity and muscular contraction force in diabetic rats;
(f) improved motor co-ordination in “wobbler mice”, which have a phenotype involving progressive atrophy of motoneurons and musculo-cutaneous nerve fibres;
(f) accelerated regeneration of the sciatic nerve in diabetic rats; and
(g) helped protect sensory neurons from Cisplatin induced lesions.
Patent PCT/US98/12545 discloses a method of increasing the metabolic rate of aged cells of a rodent host without a concomitant increase in metabolic production of reactive oxygen species. This method involved orally administering a composition of carnitine and of acetyl-L-carnitine of sufficient concentration to increase cellular metabolic process while simultaneously alleviating the resultant increase in oxidative stress. The treated animal showed host cell mitochondria with enhanced levels of cardiolipin and membrane potential, reduced production of reactive oxygen species, and mitigation of indicia of aging, including activity, muscle tone, coat appearance and kidney morphology.
Although patents PCT/IT99/00268 and PCT/US98/12545 teach use of acetyl L-carnitine and alpha-lipoic acid in combination, neither provides acetyl L-carnitine and alpha-lipoic acid in a single compound. No prior art provides acetyl L-carnitine and alpha-lipoic acid (or an alpha-lipoic acid derivative) linked to each other in a single compound by a linker that is hydrolysable intracellularly at the active site.
Further, the prior art generally contemplates administering compositions of acetyl L-carnitine or alpha-lipoic acid systemically.
All publications and patent applications cited in this specification are herein incorporated by reference as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Although the present invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be apparent to those of ordinary skill in the art, in light of the teachings of this invention, that certain changes and modifications may be made thereto without departing from the spirit or scope of any appended claims.